The present invention is directed to intraocular lenses (IOLs). More particularly, the invention relates to multifocal IOLs which are adapted to provide accommodating movement in the eye and which have reduced add powers.
The human eye includes an anterior chamber between the cornea and iris, a posterior chamber, defined by a capsular bag, containing a crystalline lens, a ciliary muscle, a vitreous chamber behind the lens containing the vitreous humor, and a retina at the rear of this chamber. The human eye has a natural accommodation ability. The contraction and relaxation of the ciliary muscle provides the eye with near and distant vision, respectively. This ciliary muscle action shapes the natural crystalline lens to the appropriate optical configuration for focusing light rays entering the eye on the retina.
After the natural crystalline lens is removed, for example, because of cataract or other condition, a conventional, monofocal IOL can be placed in the posterior chamber. Such a conventional IOL has very limited, if any, accommodating ability. However, the wearer of such an IOL continues to require the ability to view both near and far (distant) objects. Corrective spectacles may be employed as a useful solution. Recently, multifocal IOLs have been used to provide near/far vision correction. See, for example, Portney U.S. Pat. No. 5,225,858, Roffman et al U.S. Pat. No. 5,448,312 and Menezes et al U.S. Pat. No. 5,682,223. Monofocal IOLs with a depth of focus features has been suggested and are shown and described in Portney U.S. Pat. No. 5,864,378.
Another approach to overcoming loss of accommodation is to use ophthalmic lenses, such as contact lenses or IOLs, with different optical characteristics for each eye. For example with a system known as monovision one lens has a distance vision correction power and the other lens has a near vision correction power. Another example is shown and described in Roffman et al U.S. Pat. No. 5,485,228. It is also known to implant a distant dominant multifocal IOL in one eye and a near dominant multifocal IOL in the other eye as disclosed in the January 1999 issue of Clinical Sciences by Jacobi et al entitledxe2x80x9cBilateral Implantation of Asymmetrical Diffractive Multifocal Intraocular Lenses,xe2x80x9d pages 17-23.
Whether monovision or multifocal ophthalmic lenses are employed, nighttime images may not be the same for both eyes and/or possess halos as when the headlights of an oncoming vehicle are observed. This can significantly reduce the ability of the observer to identify and locate objects near the headlights. For example, halos tend to be created when the patient views a distant object through the near vision portion of the lens, and the greater the add power, the more perceptible is the halo.
For example, this is shown and described in commonly assigned application Ser. No. 09/302,977 filed on Apr. 30, 1999. This application discloses a reduced add power multifocal IOL which reduces the effects of halos. This reduced add power IOL is implanted in a phakic eye in which the natural lens has lost some degree of accommodation, i.e. in partially presbyopic eyes.
Commonly assigned application Ser. No. (Atty. Docket No.: D-2857) filed concurrently herewith also discloses multifocal reduced add power lenses, such as IOLs, which are asymmetric, i.e., have different optical characteristics. However, one of these lenses has an add power for full near vision.
The disclosure of each of the patent applications and patent identified herein is incorporated in its entirety herein by reference.
New multifocal intraocular lenses (IOLs) adapted to provide accommodating movement in the eye and which have reduced add powers have been discovered. Such IOLs are particularly useful in aphakic eyes in which the natural lens has been removed. The present IOLs have multiple optical powers, that is are multifocal, have at least one reduced add power and provide substantial benefits. The combination of a multifocal IOL with at least one reduced add power together with the ability of the IOL to move to provide accommodation very effectively provides for enhanced vision over a relatively wide range of distances, for example, from distance through near, and, in addition, reduces the size and/or occurrence of halos and other nighttime vision phenomena which can adversely affect vision.
In one broad aspect of the present invention, intraocular lenses for implantation in an eye of a patient are provided. Such lenses comprise a multifocal optic having a maximum add power which is less than the add power required for full near vision for the pseudophakic eye, that is an eye including the IOL but not including the natural lens. The maximum add power of the multifocal optic preferably is about the add power required for intermediate vision for a pseudophakic eye. In addition, a movement assembly is provided. This movement assembly is coupled to the optic and is adapted to cooperate with the eye of the patient to effect accommodating movement of the optic in the eye.
In one embodiment, the multifocal optic has add powers for providing distance and intermediate vision for a pseudophakic eye and the movement assembly provides sufficient accommodating movement of the optic to obtain near vision for a pseudophakic eye. Thus, the patient in whose eye the present IOL is implanted has a range of vision from distance through near.
As can be seen, the present IOLs utilize a combination of an optic with multifocal characteristics and a movement assembly adapted to provide accommodating movement of the optic in the eye. This combination very effectively provides vision over a range of distances. At the same time, the present IOLs reduce the size and/or occurrence of halos and other nighttime phenomena which can adversely affect the vision of the patient. Such reductions in the size and/or occurrence of one or more of such phenomena are relative to a full add power, for example, full near add power, multifocal IOL located in a fixed position, that is without accommodating movement, in the eye.
To illustrate the present invention, the maximum add power of the present multifocal optic is, for example, no more than about 1.25 diopters or about 1.5 diopters, and the movement assembly is adapted to provide at least about 1.0 diopter or at least about 1.5 diopters of accommodation. Thus, the total or maximum effective optical add power apparent to the patient is about 2.25 diopters or about 3.0 diopters or more, which is well within the range of full near vision. All of the add powers set forth herein are in the spectacle plane.
The movement assembly preferably is adapted to provide at least about 0.5 mm or at least about 0.75 mm of accommodating movement.
In one embodiment, the optic has a distance vision correction power for infinity, for example, with the optic in the rest position or in the unaccommodated state in the eye.
The movement assembly of the present IOLs can be of any configuration suitable to provide the desired accommodating movement. One particularly useful movement assembly is that shown and described in commonly assigned application Ser. No. 09/532,910, filed Mar. 22, 2000.
In one useful embodiment, the movement assembly circumscribes the optic and comprises a member including a proximal end region coupled to the optic and a distal end region extending away from the optic and adapted to contact a capsular bag of the eye. The movement assembly preferably is positioned relative to the optic so that, with the intraocular lens at rest, the optic vaults anteriorly of the distal end region of the movement assembly. In order to enhance the accommodating movement of the present IOLs, the movement assembly may include a hinge assembly positioned proximally of the distal end region.
The present intraocular lenses are preferably deformable for insertion through a small incision in the eye.
In a further broad aspect of the present invention, intraocular lenses are provided which include a multifocal optic having a range of optical powers which can provide vision for a pseudophakic eye of only a portion of the range of from distance through near. A movement assembly, coupled to the optic is provided. This movement assembly is adapted to cooperate with the eye of the patient to effect accommodating movement of the optic in the eye. The accommodating movement is sufficient to provide vision for a pseudophakic eye for the remainder of the range of distance through near whereby the patient has a range of vision from distance through near. Preferably, one of the powers of the optic is a power for distance vision, for example, a distance vision correction power for infinity, for a pseudophakic eye and another of the powers of the optic is an add power.
In a still further broad aspect of the present invention, intraocular lenses for implantation in an eye of a patient are provided and comprise an optic and a movement assembly. The movement assembly is coupled to the optic and adapted to cooperate with the eye of the patient to effect accommodating movement of the optic in the eye. The optic has a baseline optical power and at least one optical add power. The at least one optical add power has a magnitude which is reduced to take into account the accommodating movement provided by the movement assembly. Preferably, the at least one add power has a magnitude which is reduced relative to an add power of a similar optic adapted to be maintained in a fixed position in an eye.
One additional broad aspect of the present invention provides for ophthalmic lens systems for implantation in the eyes of patients, for example, in the eyes of patients whose natural lenses have been removed. Such lens systems comprise first and second multifocal optics. Each of these multifocal optics have an add power. The maximum add power of the first optic is less than the add power required for full near vision for a pseudophakic eye. First and second movement assemblies are provided and are coupled to the first and second optics, respectively. These movement assemblies are adapted to cooperate with the eyes, respectively, of the patient to effect accommodating movement of the first and second optics. The optical characteristics of the first and second optics can be identical or substantially identical or can be different.
In one embodiment, each of these optics have an optical axis. The power of each of these optics changes along a power curve, preferably in a radially outward direction from the associated optical axis. The power curve for the first optic may be different from the power curve for the second optic. Alternately, the power curve for the first optic is substantially the same as the power curve for the second optic.
In one useful embodiment, the first optic is biased for distance vision and the second optic is biased for intermediate vision.
Thus, the first optic or lens is biased for distance vision or is distance biased. This may be accomplished, for example, by configuring the first optic so that the best visual acuity provided by the optic is for distant objects, for example, objects at infinity. The first optic provides better visual acuity for objects at infinity than the second optic. Preferably, the first lens substantially optimizes visual acuity from distance to intermediate distances. The first optic has a power including a power required for distance vision correction for the pseudophakic patient.
The second optic has a power including a power required for intermediate vision correction for the patient. The second optic preferably is intermediate biased. This may be accomplished, for example, by configuring the second optic so that the best visual acuity provided by the second optic is for objects at intermediate distances. Alternatively, or in addition thereto, the second optic provides better visual acuity from intermediate to near distances than the first optic. Preferably, the second optic enhances visual acuity from intermediate to near distances. In addition to the advantages noted above, this enhanced visual acuity of the second optic significantly enhances intermediate vision and provides functional near image quality. It also minimizes potential undesirable effects by using only a low level of image quality disparity between the images received by the two eyes.
The optics or lenses can be made to have the relatively larger ranges in various ways. For example, this can be accomplished by appropriately splitting the light between distance and intermediate. Thus, the second optic may focus sufficient light to an intermediate focus region so as to contribute to the second optic providing enhanced vision from intermediate to near distances.
Alternatively or in addition thereto, the depth of focus of the zone or zones of the optic which provide intermediate vision correction may be appropriately increased to make the second optic have enhanced vision from intermediate to near distances. This may be accomplished, for example, by controlling the aspheric surface design of the optics. More specifically, the second optic may have a zone with an add power for intermediate vision correction with such zone having optical aberrations which increase the depth of focus of such zone. In one preferred embodiment, such zone extends radially outwardly and has progressively increasing add powers as the zone extends radially outwardly.
The add power of the optics is reduced over what it would be if one or both of the optics had the full or even nearly full add power required for near vision correction. The reduced add power significantly reduces halos and/or other nighttime phenomena.
In the interest of keeping the add power low while providing adequate vision quality, preferably the maximum power of any region of either or both of the first and second optics is no greater than about the power required for intermediate vision correction. By way of example, the maximum add power for both the first lens and second lenses may be from about 0.5 diopter to about 1.75 diopters and is preferably from about 1 diopter to about 1.5 diopters.
The first and second optics are adapted to provide some depth of focus. The first optic preferably provides some depth of focus toward intermediate vision correction and preferably the second lens also provides some depth of focus from intermediate vision correction toward far vision correction.
Each of the first and second optics has an optical axis. Preferably the power of the first lens is different at a plurality of locations radially outwardly of the optical axis of the first optic, and the power of the second optic is different at a plurality of locations radially outwardly of the optical axis of the second optic.
Viewed from a different perspective, the power of each of the first and second optics changes along a power curve, for example, in a radially outward direction from the associated optical axis. The power curve for the first optic is different from the power curve for the second optic. The power curve of the first optic may at least contribute to the first lens having good visual acuity from distance to intermediate distances and the power curve of the second optic may at least contribute to the second lens having good visual acuity from intermediate to near distances. Each of the first and second optics may have a power which varies from about the power required for far vision correction to about a power required for intermediate vision correction. In one embodiment, the first optic has a larger range of vision for distance to intermediate distances than the second optic. In the same or a different embodiment, the second optic has a larger range of vision for intermediate to near distances than the first optic.
In one preferred embodiment, the first optic has first, second and third optical zones arranged radially with respect to the optical axis of the first optic with the second zone being intermediate or between the first and third zones and having a greater add power than either of the first and third zones. Similarly, the second optic has first, second and third optical zones arranged radially with respect to the optical axis of the second lens with the second zone being intermediate the first and third zones and having a greater add power than either of the first and third zones of the second optic.
Although the zones can be of various configurations, they are preferably substantially annular and substantially concentric. Preferably, there are at least two zones. Still more preferably, there are three or five of the zones with the innermost and outermost of the zones having a power for far vision correction.
The power in a radial direction can change either gradually or abruptly. The maximum power in each of the second zones may be substantially the same. In one form of the invention, each of the second zones has a power which is substantially constant, and the area, for example, the annular area, of the second zone of the second optic is larger than the area of the second zone of the first optic. This also contributes to the second optic having better visual acuity from intermediate to near than the first lens.
IOLS constructed in accordance with this invention are particularly effective when implanted following removal of the natural lenses. Even though the lenses of this invention have a reduced add power, the additional accommodation provided by the movement assemblies cooperating with the eyes allows excellent visual quality from distance through near.
According to one aspect of the method of this invention first and second IOLs, for example, having different optical characteristics, are implanted in the eyes, respectively, of the patient, preferably after the natural lenses of the patient have been removed. Each of the IOLs preferably has a power required for far vision correction and a power required for intermediate vision correction power with the maximum power of each of the first and second IOLs being less than the add power required for near vision correction for the patient.
According to another feature of the method of this invention, first and second ophthalmic lenses are placed in the eyes of a patient after removal of the natural lenses with the first lens being distance biased and the second lens being intermediate biased.
Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.